Compressor unloader



Feb. 26 1924. 1,484,673

s. B. REDFIELD COMPRES SOR UNLOADER Fi y '16. 1923 3 Sheets-Sheet 1 'NVENTOR howdenflfled z'eld.

ms ATTOR Y Feb. 26 1924. 1,484,673

' v s. a. REDFIELD COMPRESSOR UNLOADER lfiled May 16.1923 5 Sheets-Sheet 2 QNVENTOR BY i H IS ATTOR Y Feb. 26 1924. 1,484,673-

s. B. REDFIELD COMPRESSOR UNLOADER Fil d May 16. 1923 3 Sheets-Sheet 3 drawings.

. sure on both sides of the .and

- oration is Patented Feb. 26, 1924.

UNITED STATES SHOWDEN' B. anon-m1), 0F EABTOH,

COMPANY, OF JERSEY CITY, HEW

VAIIIL, ASSIGHOB T0 menasonnnann A CORPORATION OF NEW JERSEY.

common LOADED.

- Application lied n1 is, use. some Io. sauna.

To all whom it may concern:

Be it known that I Snownmt B. Ram the IJnitcd States, a resimam, a. citizen of county of Northampton,

dent of Easton, and State of-Pennsylvania have invented a certain Compressor Unloader, of which the following is a. specification accompanied by This mvention relates compressor unloaders, but more particularly to an pnloader for relieving the fluid compression load, during the period of 1starting. 'The compressor may be operator or instance by an electric motor, started automatically and stopped b' means of an automatic pres sure controlle electric switch, but my unloader preferably has no connection with the control switch, and the unloading opormedonly'by the adionof the compressor itself.

The objects of the to reduce an im roved means for positive y controlling e starting period 0 the compressor, so that the load will not be thrown on the compressor until a predetermined speed of thecompressor piston has been reached, and for permitting theprescompressor piston to be relieved asthe com ressor stops.

To these and other on which will hereinafter appear, the inven on consists of the apparatus shown in one of its preferred forms in the accompanying drawings, in which Figure 1 is a vertical sectional view of a V compressor unit, with the unloader and pilot valves connected thereto showing tion the rts assume when the comprmsor is under oad.

Figure 2 is an detail view partly o the choking needle in vertical section valve, 7 3isa-viewsimilartoFigure'1 showing the position the parts when thecompressor ls-etarting or stopping, and

the compressor piston is moving to the left,

in as drawinge theunloeder A H. to thedrschargollneBofa C the compressor and p invention are preferably carried by a the agmst seat-by the com the usual receiver D. The compressor comprises the c linder E having the reciprocating piston adapted to be driven by any suitable source of power, as an electric motor not shown); The com ressor is provide with the inlet valves the discharge valves H, and the discharge chamber J, connected to the discharge line B.

The unloader comprises the valve casing K the main valve chamber L'separatedfromtheoutletOlzya on which the main check V vs 18 adapted to be seated for controlling the discharge from the using. The check valve Q is provided with the spring R on valve and held by the ca S, which cap also forms a valve 'de. e are m the receiver tank normally holds the main cheek yalve Q to its seat when the compreschamber L and atmospheric vent X, conveniently located in the side of the extenslon Y of the main casi'nfi hK, in which the relief valve -V operates. e relief valve V piston Z and has limited lonfiudinal movement relatively to h Piston,

iaton Z by a comparatively inthevalvesocket ,of

coil

relief valvefrom o thesp' Thevalveisheldtoits spring pressure and fluid premur'e d the piston Z. The mot of the bythepinc l-ts sl aperturedinthoendinthepistonz.

Thepiston 'al provided with an enlarged head transverse artition P relief valve V is them urged outwardlmrom the r head is shut oil and prevented. The relative longitudinal movement or lost motion connection provided between the relief valve V and the piston Z enables both the valve and the piston to be tightly seated on their seats U and 7 respectively.

A projection or stop 9 on the piston Z is adapted to bear against an adjusting screw h in the cap W by means of which the initial startin position of the (piston Z and relief valve V may be adjuste The unloader so far described prevents the fluid com ressi load from coming u on the,mach1ne until the motor is up to ull speed. During the starting period fluid, as air, enters the main valve casing K at the inlet side and leaves at the atmospheric vent X, and the main check valve Q holds back the air in the receiver D and pipe lines. When the compressor is started, the sli ht ressure built up in the main valve chain r will force both the relief valve V and piston Z outwardly and substantially all the air will pass through the vent X to atmosphere. It is to be assumed that the adj ustmg screw h has been set at such a point that the relief valve and piston move rearwardly and open the relief valve the required amount, so that when the compressor is up to full speed, there will be a throttling pressure of a few pounds as the air passes the relief valve V.

The loadin should be delayed until substantially full compressor speed is reached, and the unloading should occur automatically inst as or before the compressor stops entire y. In order to make the unloader A operate positively on starting and to relieve t e pressure on both sides of the compressor piston F as the compressor stops, I provide a plurality of pilot valves, which are connected to the compressor cylinder and in series with the unloader.

In this instance, the pilot valves A and B are connected by pipes 3 to the com ressor cylinder adjacent each end thereof? A pipe or tube j connects the extension Y of the valve casing rearwardly of the piston Z with the port is in the upper section of the ilot valve B in order to admit pressure fluid to or relieve it from the rear of the piston Z, as required. The ilot valveA' IS in communication with t e main valve chamber L through the pipe or tube As shown in Figure 2, a choking needle valve p chokes or throttles the flow of pressure fluid from the main valve chamber L through the tube. 0, and may be adjusted to delay the loading point. A lock nut the needle valve in a set position. A tube r afiords communication between the two ilot valves,and is connected to the top Q the pilot valve B and to the port In in the pilot valve A. The unloader and are connected inseries and the advantage check valve 1: spaced gholds b pilot valves of such a connection is that the ressure in the compressor c linder on both sides of the piston is relieve on stopping, and the load 18 not thrown on the com ressor on starting until the predetermined speed has been reached.

The pilot valves A and B are identical in their construction, and each is composed of an upper section m and a lower section :12, held together in any suitable manner, as bolts and nuts. check valve 8 is adapted to be moved to its seat It by a coiled s ring u and controls the flow of pressure uid throu h the upper casing section as. An u wardiy seating ball rom the ball check valve 8 by the spacer pin 7 is adapted to be moved to its seat to by a plunger 2 to control the passa e of pressure fluid to atmosphere through the port or vent 8.

The plunger, 2 has limited movement in the piston 2 over a pin 3 passin through the transverse aperture 4: in the p un er. The ends of the pin 3 are secured in t e piston 2. A comparatively heavy coiled sprin 5 urges the plunger .2 forwardly, so that w en the piston 2 is moved to its seat 6 in the easing :12, the plunger a will move the ball valve 1: to its seat to. When the ball valve 0 is moved to its seatw, the ball valve 3 is accordingly moved from its seat 25 by the spacer pin 7. Thus, when one of the ball valves is seated, the other is unseated.

The check valve 9 therethrough, controls the outlet of pressure fluid from the lower casin section a: to the compressor cylinder. A coil spring 11 serves as a distance piece for the check valve 9, so that the valve will not be moved too great a distance from its seat.

When the compressor starts or sto s, and the compressor piston is moving to t e left, as shown in Figur 3 of the drawings, the pressure fluid from he com ressor cylinder moves the piston 2 of the pi ot valve A u wardly to seat the check valve '0, and y means of the spacer pin 7 unseats the chec valve 8. Pressure fluid may then pass from the main valve chamber L through the pipe or tube 0 into the pilot valve A, ast the check valve 8 and spacer pin 7, an to the pilot valve B through the pipe or tube 1'. As the cclngpressor piston F is on its suction stroke, pressure fluid passes from the lower section as of the ilot valve B" to the com ressor cylinder t rough the pipe y. The piston 2 in the pilot valve B is moved downwardly y the action of the coil s ring u, and entrance of atmospheric air t rough the port '8 in the casing section at. The check valve a is seated at the same time by the coil spring u, there shutting off the assage of pressure flui from the valve clihmber L. The check valve 1: is accordingly unseated, so

b .A downwardly seating ball having a small port 10 ative to the pilot valve B,

6 the right on starting or sto that the assage through the i or tube is o n to atmosphere throu glfihe vent g in t e pilot valve casing B.

When the compressor piston is moving to ing, as shown in Figure 4, the operation 0 t pilot valves A and B justdescribed is reversed. In this instance, the pressure fluid behind the piston Z in the extension Y of the discharge valve casing passes to atmosphere through the vent 8 in the pilot valve The check valve 1) in the pilot valve B is seated by the piston 2, which is moved upwardly by pressure fluid admitted from the compressor cylinder into the casing section an, and closes the atmospheric vent 8. The check valve 8 is unseated at the same time, and fluid is permitted to pass through the pipe or tube r to the ilot valve A to be vented to atmosphere t rough the port 8 in the casing section as. In either irection the compressor piston F moves on starting and etc ping, a differential pressure is created in t e compressor cylinder, and by means of the pilot valves, connected in series, the pressure fluid behind the unloader piston Z is vented to atmoshere, and passage of fluid from the main valve chamber L to the piston Z is shut off and prevented.

Durin the time that the compressor is accelerating, the alternate risin and falling of the pistons 2 in both pilot va ves will continue until the compressor piston F has at tained such a speed that there is insuflicient time during the suction stroke of the piston F, relative to each pilot valve alternately, for\ the pressure flmd in the spaces under the pistons 2 in each pilot valve A and B to escape through ports 10 in the check valves 9 to the compressor cylinder. When this condition has been reached, the pressure in the s ace under the .pistons 2 in each pilot vaFve will be suflicient to hold the pistons 2 in each ilot valve in the extreme upward position ughout the normal runnmg period of flit-compressor. When the pistons 2 are in the upward position, the check valves '0 in each plot valve are seated and check valves fill each pilot valve are unseated. Thisallows pressure fluid to flow from the main valve chamber. L through the pipe or tube 0, past the check valve 8 and spacer pin L 7 in the pilot valve A,

5 through side outlet K to the pipe or tube 1', past'the check valve 8 and spacer pin 7 in the pilot valve B, through the port through the pipe or tube 7' to the extenion Y of the main valve casing. The pressure fluid forces the piston Z inwardly, and moves the relief valve V to its seat U, thus shuttin oil the flow of air from the main valve 0 amber L through atmospheric vent X. Further increase of pressure back of the piston Z com resses the spring a, moving the enlarged sad 6 of the piston Z to its sure therein to such a point as to overcomethe spring R and fluid pressure in the discharge pipe 0 and receiver D. -The check valve Q is then raised and pressure fluid is discharged from the compressor into the discharge pipe 0 and the receiver D, thus performing useful work. Further delay in the closing of relief valve V, in order to allow the compressor to attain higher speed before taking up its load, is secured by screwing in on the choking needle valve p as shown in Figure 2. a

On stopping of the compressor during the slowing down of the iston F, suflicient time will be allowed on t e suction strokes relative to each pilot valve, to allow the air under the pistons 2 to be discharged through port 10 inthe check valves 9. This will alow the pistons 2 to move down to unseat the check valve '0, and reseat the check valve 8. This action takes place alternately in the two pilot valves on alternate suction strokes. The unseating of the check valves 0 allows the pressure fluid from behind the piston Z to be discharged through the pipe or tube 7' to atmosphere through the vents 8 in the two pilot valves alternately with each suction stroke, and at the same time shuts oil the passage of pressure fluid from the main valve chamber L by the alternate closing of check valves 8 in the two pilot valves. This is substantially the same action as was described for the starting period of the com pressor.

The unloader should be adjusted to unload as promptl as possible on stopping. To this end, was ers 13' are provided in the lower sections of the pilot valves, by which the volume under the pistons 2 may be varied. With high pressures, there is too great a volume of air under the pilot valve pistons 2 to permit quick passage thereof through the small port 10 in the check valves 9, for the compressor to unload on stopping. It is therefore necessary to remove the lower section of the pilot valve casings and insert a greater number of washers 13 therein in order to reduce the volume into which pressure fluid may enter. On the other hand, with low pressure, it is neces sary to increase the volume in the lower section of the pilot valve to prevent unloading durin the running period, and to delay unloa ing while slowing down. To do this, the number of washers is reduced. A screw 14 is threaded into the upper section of the ilot valves, and extends into the exteral circumferential groove 15 in the pistons 2, and serves to prevent the parts from falling out when the lower section of the pilot valve is removed for adding to or removing washers from the lower section.

By means of the ilot valves and unloader, connected'toget er in series, all the pressure fluid remaining in the compressor cylinder, when the compressor stops, passes to atmosphere through the vent X in the extension Y of the main discharge valve casing, thereby relieving the compressor from load, until it has again attained substantially full speed. i

I claim:

1. The combination with an unloader adapted to be connected to the discharge line of a compressor, of a plurality of pilot valves connected in series with the unloader and connected to the compressor cylinder adjacent each end thereof, whereby pressure on both sides of the compressor piston is relieved on stopping.

2. The combination with an unloader adapted to be connected to the discharge line of a compressor, of a plurality of pilot valves connected in series with the unloader and connected to the compressor cylinder adjacent each end thereof, whereby the compressor remains unloaded until a predetermined speed has been reached.

3. The combination with an unloader adapted to be connected to the discharge line of a compressor, of a plurality of pilot valves connected in series with the unloader and connected to the compressor cylinder adjacent each end thereof, and means for varying the time of unloading, whereby pressure on both sides of the compressor piston is relieved on stopping.

4.. The combination with an unloader adapted to be connected. to the discharge line of a compressor, valves connected in series with the unloader, and a piston in each pilot valve, controlled by the pressure in the compressor cylinder and means for controlling the amount of fluid admitted to the pistons.

5. The combination with an unloader adapted to be connected to the discharge line of a compressor, of a plurality of pilot valves connected in series with the unloader, a check valve in each pilot valve controlling an atmos heric vent, and a iston for seating said 0 eck valve, controlled by the pressure in the compressor cylinder.

6. The combination with an unloader adapted to be connected to the discharge line of a compressor, of a plurality of pilot valves for operating said unloader and connected in series therewith, comprising a casing, and check valves in the casing actuated in one direction by the ressure in the compressor cylinder, where unloading of the compressor is controlled y the speed of the compressor iston, and the compressor remains unloa ed until a predetermined speed has been reached.

of a plurality of pilot.

7. The combination with an unloader adapted to be connected to the discharge line of a compressor, a piston in the unloader, of a p urality of pilot valves controlling the movement of said piston, and connected in series with the un oader, and means associated with the pilot valves for varying the time of unloadin whereby the pressure on both sides of t e compressor piston is relieved on stop ing, and the compressor remains unloade until a predetermined speed has been reached.

8. The combination with an unloader adapted to be connected to the discharge line of a compressor, of a plurality of pilot valves connected in series with the unloader, a plurality of check valves associated with the pilot valves and means controlled by the ressure in the compressor cylinder'for seating and unseating said valves, whereby the pressure on both sides of the piston is relieved on stopping, and the compressor remains unloaded until a predetermined speed has been reached.

9. The combination with an unloader adapted to be connected to the discharge line of a com ressor, and a valve in the unloader contro ling an atmospheric vent, of a plurality of pilot valves connected in sense with the unloader, and means associated with said ilot valves for varying the time of unloa ing, whereby the pressure on both sides of the piston is relieved on stopping, and the compressor remains unloaded until a predetermined speed has been reached.

10. In combination, an unloader adapted to be connected to the discharge line of a compressor, comprisin a valve casing having a main valve cham er, a main discharge va ve controlling the outlet from said chamber to the discharge line, a vent to atmosphere from said chamber, an automatic relief valve controlling the vent to atmosphere and actuated both to open and close by fluid pressure, the main discharge valve until the compressor has attained sufiicient speed to permit the load to be safely thrown on the compressor, and pilot valves connected in series with the unloader, whereby pressure on both side of the compressor piston is relieved on stopping. v

11. In combination, an unloader adapted to be located in the discharge line of a compressor, comprisin a main valve casing, a main dischar a va ve controlling the outlet from said casing to the discharge line, an ex; tension on the main valve casing, a vent to at mosphere from said extension, an automatic relief valve controlling the vent to atmosphere and actuated to both open and close by fluid pressure, thereby preventing the opening of the main discharge valve until the com pressor has attained suflicient speed to perthereby preventing the opening of mit the load to be safely thrown on the compressor, and-pilot valves connected in senes with the unloader and to the compressor cylinder adjacent each end thereof, check valves associated with said pilot valves, and means for seating one of said check valves controlled by the pressure in the compressor cylinder.

12. In combination, an unloader adapted to be connected to the discharge line of a compressor, comprising a main valve casing, a main discharge valve controlling the outlet from said casing to the discharge line, an extension one-the main valve casing, a valve in said extension controlling a vent to atmosphere, and pilot valves connected in series with the unloader and the confpressor cylinder adjacent each end thereof, each of said pilot valves comprising a casing, a plurality 0 check valves in the casing, means controlled by the cylinder for seating one of said valves, said valves being so arranged that when one is seated the other is unseated, and means for varying the time of unloading, whereby the pressure on both sides of the piston is automatically relieved on stop ing, and the compressor remains unload until a predetermined speed has been reached.

In testimony whereof I have signed this 80 specification.

' SNOWDEN B. REDFIELD.

pressure in the compressor 

